$username = "<domain>\<username>"
$password = ConvertTo-SecureString "<password>" -AsPlainText -Force
$cred = New-Object System.Management.Automation.PSCredential -ArgumentList ($username, $password)
# Invoke Command on a VM using creds
invoke-command -vmname <vmname> -credential $cred -scriptblock {whoami}
Enter-PSSession -VMName <vmname> -Credential $cred